IB/core: disable memory registration of filesystem-dax vmas

Until there is a solution to the dma-to-dax vs truncate problem it is
not safe to allow RDMA to create long standing memory registrations
against filesytem-dax vmas.

Link: http://lkml.kernel.org/r/151068941011.7446.7766030590347262502.stgit@dwillia2-desk3.amr.corp.intel.com
Fixes: 3565fce3a6 ("mm, x86: get_user_pages() for dax mappings")
Signed-off-by: Dan Williams <[email protected]>
Reported-by: Christoph Hellwig <[email protected]>
Reviewed-by: Christoph Hellwig <[email protected]>
Acked-by: Jason Gunthorpe <[email protected]>
Acked-by: Doug Ledford <[email protected]>
Cc: Sean Hefty <[email protected]>
Cc: Hal Rosenstock <[email protected]>
Cc: Jeff Moyer <[email protected]>
Cc: Ross Zwisler <[email protected]>
Cc: Inki Dae <[email protected]>
Cc: Jan Kara <[email protected]>
Cc: Joonyoung Shim <[email protected]>
Cc: Kyungmin Park <[email protected]>
Cc: Mauro Carvalho Chehab <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: Seung-Woo Kim <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Cc: <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

drivers/infiniband/core/umem.c

@@ -191,7 +191,7 @@ struct ib_umem *ib_umem_get(struct ib_ucontext *context, unsigned long addr,
 	sg_list_start = umem->sg_head.sgl;
 
 	while (npages) {
-		ret = get_user_pages(cur_base,
+		ret = get_user_pages_longterm(cur_base,
 				     min_t(unsigned long, npages,
 					   PAGE_SIZE / sizeof (struct page *)),
 				     gup_flags, page_list, vma_list);